Evaluation of UASB/CO₂ stripping system for simultaneous removal of organics and calcium in linerboard wastewater

Abstract

A combined upflow anaerobic sludge blanket (UASB) and CO₂-stripping system was evaluated for its capacity to simultaneously remove organic compounds and calcium from linerboard mill wastewater. A continuous-flow UASB has significant potential to remove organic compounds, and its removal efficiency is closely related to volumetric organic loading. After the UASB process, a gradual decrease of pH was observed and CO₂-stripping indicated the formation of acid/methane and carbonate. The high concentration of carbonate that was generated from the elevated pH of the CO₂ stripper easily reacted with calcium in the wastewater to form a solid-phase calcium carbonate. The significant amount of methane that was produced during the UASB process implies that methane-producing bacteria dominate the microbial composition of the reactor. In the CO₂ stripper system, calcium removal and alkalinity consumption rose simultaneously with increasing solution pHs. This result suggests that the combined activity of the UASB reactor and the CO₂ stripper system is a powerful tool for removing organic compounds and calcium from linerboard wastewater. Such a system would allow water from the linerboard production process to be reused and be discharged with fewer toxic compounds. © 2010 American Institute of Chemical Engineers Environ Prog, 2011